1. Field of the Invention
The present invention relates to an encapsulated semiconductor module which includes electronic components such as IC chips.
2. Description of the Related Art
FIG. 7 is a plan view showing a conventional semiconductor module. A large number of wiring layers of a metal thin film are provided on a flexible film 73, and two IC chips 75 having bumps (not shown) of solder or gold are mounted on the wiring layers 74.
FIG. 8 is a sectional view showing the connection between the IC chip and the wiring layers by means of TAP (Tape Automated Bonding). That is, the IC chip 75 is electrically connected to the wiring layers 74 through bumps 76, and the wiring layers 74 are electrically connected to external leads (not shown).
Since each of the wiring layers 74 used for the TAB is thin, the current capacity thereof is small. However, since a relatively large current is required for the semiconductor module, the current capacity may be reduced. In addition, since the IC chips 75 are only compression-bonded to the wiring layers 74 through the bumps, the contact areas of the IC chips 75 to the flexible film 73 become small. For this reason, each of the IC chips 75 has poor heat dissipation.
FIG. 9 is a plan view showing another conventional semiconductor module. This support member includes a plurality of leads 70 made of a metal plate, and islands 71 unitary with the leads 70. An IC chip 78 and circuit components 72 such as power MOS devices and other discrete semiconductor devices are mounted on the islands 71, respectively. A part of each of the leads 70, the circuit components 72, and the IC chip 78 are molded with a plastic material PC.
The support member is formed of a metal, e.g., copper, provided by etching or punching. The IC chip 78 and the circuit components 72 are electrically connected to the leads 70 through bonding wires 79.
However, in the above semiconductor module, the structure is complicated when the number of chips is increased.
FIG. 10 is a plan view showing still another conventional semiconductor module. Provided on a support substrate 80 are wiring layers 81 of copper, chip type electronic components 82 such as capacitor, resistor, etc., a printed resistor 83 whose resistance value is finely adjusted by trimming, and IC chips 84 mounted on the support substrate 80. The IC chips 84 are electrically connected to the wiring layers 81 by bonding wires 85, and the wiring layers 81 are electrically connected to leads (not shown).
The support substrate 80 is formed of an insulating plate or a plate having a surface subjected to insulation treatment. For carrying out the insulation treatment, an insulating film is adhered to the plate, or the plate is coated with an insulating coating. The wiring layers 81 are formed by bonding a metal plate on the support substrate 80 and etching it, by bonding an etched frame on the support substrate 80, or by printing a conductive resin paste on the support substrate 80.
Even in the above semiconductor module, since the thick wiring layers 81 are formed on the support substrate 80, the occupying area of the wiring layers 81 is increased. In addition, the wiring layers 81 are complicated as the number of chips is increased. For this reason, the occupying area of the wiring layers 81 is larger than that of the chips, thereby increasing an area per one chip in the semiconductor module. That is, the area efficiency is degraded.
In any case, in each of the above conventional semiconductor modules, since the thick wiring layers are provided on the substrate, the occupying area of the wiring layers is increased. In the case of the wiring structure connected by TAB, the current capacity is low, and the contact area between the substrate and the IC chip is small. For this reason, the IC chip has poor heat dissipation.